This invention relates to braid production, and more particularly to a former ring used in braid production.
Braid is typically manufactured using a system of equipment including a braiding machine, a forming device, including a former ring, and a take-up device. The braiding machine-consists of a track plate and yarn carriers. The yarn carriers carry the spools of yarn and use tension controls to release the yarn during processing. Half of the yarn carriers are driven in a clockwise direction and half are driven in a counterclockwise direction. The movement of carriers is guided by the track plate that causes the two sets of opposing carriers to travel in a Maypole fashion. At the point where the yarns consolidate to form the braid (called the fell, braid point, or lock point), a former device is often used to control the dimension and shape of the braided fabric. Traditionally, the former device is a ring that controls the outside diameter of the finished product, a mandrel that controls the inside diameter of the product; or a combination of a ring and a mandrel. The tension required to pull the yarn off of the carrier and to pull the finished braid is supplied by a take-up device. The take-up device applies the force by pulling on the finished braid.
A traditional former ring is a rigid plate containing a specific hole elevated above the track plate and located along the central axis of the plate. FIG. 1 shows a braiding machine braiding yarns and including a former ring. The former ring has two features that impact the formation of the braid: the diameter of the former ring relative to the cross section of the produced braid and the distance between the former ring and the track plate. The relationship between the diameter of the former ring and the cross section of the braid is most significant when the braid is produced on a mandrel because the braid formation is impacted by both the former ring and the mandrel. The former ring is the initial contact point for the yarns as they are braided and the mandrel is the final contact point. Where there is no mandrel, the braid forms naturally based on support by the former ring at the fell point. The optimal relationship is where there is a former ring and a mandrel is to minimize the distance between them. More particularly, the former ring inner diameter is ideally just larger than the outer cross section of the mandrel. For example, the difference in diameter of the outside of the mandrel and the inside of the former ring is on the order of about xc2xcxe2x80x3 or less. Where the mandrel and ring are oriented as concentric circles with common radii, the difference is about xe2x85x9xe2x80x3 or less between a radial point on the outer circumference of the mandrel and a radial point for the same radius on the inner diameter of the former ring. In this way, the former ring pushes the braided yarn a short distance to the mandrel with a short path of travel so that braid is pulled tightly against the mandrel, thereby producing a braid with the highest achievable integrity. In addition, the former ring distance from the track plate forces the fell of the fabric to be consistently created at a given distance from the track plate and, thus, enables the creation of a uniform fabric. Traditional former rings include a predetermined and non-adjustable inner diameter. However, such traditional former rings can often be adjusted to change the distance between the former ring and the track plate.
The rigid nature of the inner diameter of traditional former rings enables the creation of a braid with a uniform diameter. However, such former rings also are limited by providing only a predetermined diameter control to the braiding machine. This limitation impacts braid production in several ways. First, braiding machines are generally multi-use machines in that they are used to produce braids with a variety of diameters. Where the diameters change and a former ring is used, the braiding machine must be refitted with a separate former ring. This reduces efficiency in take-down and set-up time for orienting braiding machines for various braids. More particularly, the braiding machine was originally developed to produce many items that require continuous or repetitive braiding operations. Therefore, many changes have to be made to the machine itself for each braid production.
Second, another way that the rigid inner diameter of traditional former rings impacts braid production is with particular braids that have varying cross sections along their length such that the diameter of the braid varies. In order for traditional former rings to be used to produce such braids, at the point of the diameter change, the braiding machine operation must be suspended and the former ring must be replaced with a new former ring with a different diameter. During this exchange, yarn at the location of the former ring may no longer be supported by the ring such that the yarn orientation can change or the braid point can be lost resulting in defects in the braid, an unwinding of the braid produced prior to the exchange or an undesired fiber orientation with respect to the axial position of the braid. As a result, the quality of the braid may be reduced.
Another approach for a former ring to support a braid having a varying cross section is for the former ring to have a diameter that is larger than the largest diameter of the intended braid. More particularly, where a mandrel with a varying cross section is used, the former ring can have a diameter that is slightly larger than the largest cross section of the mandrel. However, for the areas of the mandrel for which the cross section is smaller than the largest cross section, the distance between the inner diameter of the former ring and the outer cross section of the mandrel will no longer be optimized. As a result, the integrity of the braid along the length of the mandrel varies based on the distance of the mandrel from the former ring.
Another aspect of application of a braid to a mandrel is the formation of a two-layer braid on the mandrel. One traditional approach is to apply a single layer of braid to the mandrel based on the mandrel""s vertical movement in one direction. Then, at the point on the mandrel where the second layer is to begin, a winding is manually applied over the braid on the mandrel in order to secure the braid against the mandrel. The manual operation may include, for example, physically wrapping a yarn material around the braid over the mandrel and securing it at the completion of winding or taping the braid to the mandrel, etc. The winding may include, for example, carbon fiber, aramid fiber or any other filament with adequate strength. In this way, the braid can be locked onto the mandrel. The manual winding process requires an off-line process (i.e., outside the automated braiding process) subject to manual errors and separate set-up and take-down time for the process as well as off-line processing time to actually apply the winding. In addition, the quality of the manual operation is dependent on the quality of the particular operation and is not consistent for future braid production.
Hence, there is a need for a former ring that overcomes the above described limitations of traditional former rings having rigid inner diameters and for a device to overcome the limitations of the approach described above for applying multiple layers of braid to a mandrel.
It is an object of the present invention to provide a former ring that reduces the take-down and set-up time for orienting braiding machines for various braids.
It is an object of the present invention to provide a former ring that can support braid production for a mandrel with a varying outer cross section without exchanging the ring during production.
It is an object of the present invention to provide a former ring that can support braid production for a mandrel with a varying outer cross section without the resulting braid having varying integrity along its length.
It is an object of the present invention to provide a device to overcome the limitations of a winding device for use in the application of multiple braid layers to a mandrel.
According to the present invention, a former ring may include an adjustable inner diameter that can be changed in an automated fashion. The adjustable forming ring may change diameter in order to accommodate changes in the cross section of a mandrel onto which the braid is produced or to expedite speed of set-up or take-down for braiding machines based on a variety of braid geometries, including braids with a constant or variable cross sections.